This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-247867, filed Sep. 1, 1999; and No. 11-277245, filed Sep. 29, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a camera and a distance measuring apparatus used in the camera, and more particularly to a camera for conducting a photographing operation suitable to night scenes by judging the night scene and to a distance measuring apparatus attached on a camera for taking photographs such as night scenes or the like, the apparatus discriminating a major image to be photographed within the detection screen thereby making it possible to conduct a highly precise focus detection processing with certitude at a distance measurement point at which discriminated main image to be photographed is located.
Conventionally, a large number of cameras have been developed which are designed to facilitate the photography of night scenes.
For example, Jpn. Pat. Appln. KOKAI Publication No. 7-199039 discloses a camera which is capable of photographing night scenes when a photographer sets the mode of the camera to a night scene mode at the time of photographing night scenes.
In this camera, a focus adjustment (an auto-focus, hereinafter abbreviated as AF) is conducted by projecting auxiliary light to the object to measure the distance to the object.
Furthermore, conventionally, with a camera or the like for conducting photographing operation, such as a camera or the like for photographing a desired image by exposing the image to be photographed by using films for photography, various kinds of technology are proposed for discriminating the main image to be photographed within the range of the photograph scenes in order to conduct an AF operation with respect to the main image to be photographed.
For example, in the camera disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-249369, when a detection has been made on the fact that an image signal based on an image of the object which is obtained with an electric charge accumulation type image sensor (an AF sensor) for a focus adjustment is separated into a distribution of a high luminance portion and a distribution of a low luminance portion, judgment is made that the screen constitution is such that the main object such as a person or the like is located against a bright background.
Then, in such a case, the integration time of the AF sensor is set to be long, so that a focus detection processing is conducted with an emphasis on the low luminance portion by conducting the integration calculation processing again.
In other words, in the camera technology disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-249369, in the case where the pixel data of the AF sensor is distributed in a state divided into a high luminance portion and a low luminance portion, judgment is made that the pixel data is a person against a bright background, so that the integration time of the AF sensor is prolonged to conduct the integration again thereby conducting an AF detection with an emphasis on the low luminance portion.
In such technology, an automatic focus adjustment operation is conducted with certitude with respect to the main image to be photographed such as a person or the like free from an influence of the brightness (luminance) of the background.
However, in the camera disclosed in Jpn. Pat. Appln KOKAI Publication No. 7-199039, there is a problem that it is troublesome for photographers to set the mode of the camera to the night scene mode in accordance with the scene to be photographed.
Furthermore, in the camera described in Jpn. Pat. Appln KOKAI Publication No. 5-249369, the luminance is detected with one line sensor, so that there arises a problem that the detection area is narrow, and a high contrast object is erroneously recognized, and at the same time, another problem arises that night scene cannot be discriminated when a bright area comes into the detection area.
Furthermore, the means disclosed in Jpn. Pat. Appln KOKAI Publication No. 5-249369 is constituted in such a manner that a focus state is detected with a pair of line sensors with the result that there arises a case in which, for example, a high contrast object, namely an object image with a large luminance difference is erroneously recognized because of the narrow detection area as an object in which the high luminance portion and the low luminance portion are distributed.
In such a case, it follows that a secured AF detection processing cannot be conducted on the side of the camera.
Furthermore, when the high luminance portion does not come into the detection area, judgment is made on the side of the camera that the screen is constituted in such a manner that the main object is located against a bright background.
In such a case, the desired main object is erroneously recognized on the side of the camera, so that the detection result cannot be obtained and the focus detection processing is repeated in some cases.
As a consequence, on the side of the camera, it takes a long time from the release instruction until exposure operation is conducted via the focus detection processing. Thus, the so-called release time lag is increased, which becomes a cause of hindering the operability of the camera.
Furthermore, in this case, there might be generated a case wherein the focus detection result cannot be obtained, namely the state in which the distance cannot be measured might be generated.
An object of the present invention is to provide a camera which is capable of conducting a photographing operation suitable to night scenes by automatically judging the night scene without setting by photographers.
Another object of the invention is to provide a distance measuring apparatus of a camera for discriminating with certitude the position of a main object within the photographing screen, and, at the same time, conducting a high precision distance measuring processing by conducting with certitude focus detection processing with respect to the desired image of the main object.
In order to attain the above object, according to the present invention, there is provided a camera comprising:
a pickup element
an judging section for judging whether or not a scene to be photographed is a night scene on the basis of an output result from the pickup element; and
a setting section for setting a photographing mode in accordance with the judgment result of the judging section.
Furthermore, according to the present invention, there is provided a camera comprising:
a pickup element for photographing an image of an object;
an analog/digital (A/D) converter for A/D converting an output of the pickup element; and
a processing section including a night scene judging section for judging whether or not a scene to be photographed is a night scene on the basis of a digital image signal output from the A/D converter.
Furthermore, in order to attain the other object described above, there is provided a distance measuring device of a camera comprising:
a pickup element;
a luminance distribution calculation section for calculating a luminance distribution within a screen to be photographed on the basis of an output of the pickup element;
a continuous region detection section for detecting a region where the luminance within a predetermined range continues on the basis of an output of the luminance distribution calculation section;
a main object specifying section for specifying, on the basis of the detection result of the continuous region detection section, a main object out of regions in which the luminance within the predetermined range; and
a distance measurement calculation section for calculating the distance measurement with respect to the main object which is specified with the main object specifying section.
Furthermore, according to the present invention, there is provided a distance measuring apparatus of a camera comprising:
an area sensor to be used for an auto-focus;
a first judging section for judging whether or not a scene to be photographed is a night scene or not, on the basis of an output of the area sensor;
a second judging section for judging whether or not the scene is a reverse light scene in the case where judgment is made that the scene to be photographed is not the night scene;
a main object specifying section for specifying the main object in the case where judgment is made that the scene to be photographed is either the night scene or the reverse light scene with the first judging section or the second judging section; and
a distance measurement calculation section for calculating the distance measurement with respect to the main object which is specified with the main object specifying section.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.